The present invention relates to a waterproof, weather-resistant and substantially non-stretching textile, and in particular to a substantially non-stretching, tension-resistant cloth coated with a weather-resistant synthetic substance.
It is previously known to coat textiles with some synthetic substance suitable for this purpose. The following polymers, among others, have been used as coating substances for textiles: polyurethane, polyvinyl chloride and its copolymers, polyethylene, copolymer of ethylene and vinyl acetate, esters and copolymers of polyacrylic acid, polyamides, synthetic rubber and its copolymers, and silicon rubber. A continuous polymer film can be formed from a polymer dissovled or dispersed in a organic solvent, when the solvent is evaporated from the system, or, alternatively, the polymer can be applied to the textile in the form of an aqueous dispersion, whereby a continuous polymer film is formed on the textile when the water is evaporated from the dispersion. Thermoplastic polymers can also be added in the molten state.
A textile can be made waterproof by forming a continuous polymer film on the textile. The strength properties of a coated textile depend primarily on the material selected for the base cloth, the thickness of its yarn, the yarn density in the warp and in the weft, and the weave. By a suitable selection of these, a textile is obtained which has the desired strength values and which does not in use substantially stretch under loading. However, a cloth of this type is not as such waterproof and weather-resistant. Waterproofness is obtained by coating the textile with some suitable synthetic substance and, if elasticity is required in the product, for example, an ability to be rolled, the polymer used for the coating must be flexible, i.e. stretching. This property can be achieved by means of a polymer formed even from one monomer type, but usually the desired properties are achieved by using copolymers formed from different monomers. The polymer can be given additional softness and flexibility by using so-called external softeners.
From the publication Textilveredlung, VEB Fachbuchverlag, Leipzig, 1981, 1. Auflage, it is known to form numerous coatings for textiles, and it is stated that coatings prepared from aqueous dispersions of polyurethane do not have properties as good as have the solvent-based coatings, but their importance is increased by the elimination of the disadvantages caused by solvents. In addition it is stated in the publication that only a few polyacrylates have importance as textile coating substances.
It is also previously known to coat a glass-fiber fabric with an aqueous dispersion of polyurethane, whereby a very strong and waterproof textile is obtained. The greater the demands set on the weather-resistance of such a product, the more expensive is the polyurethane dispersion to be used. The total price of the product then tends to rise very high, since polyurethane dispersion is required in a relatively large quantity to fill the pores in the textile to the effect that a completely waterproof product is obtained.
There are also known other synthetic substances by means of which especially good weather-resistance is produced. Other such substances are aromatic polyimides, the manufacture, properties and uses of which are described in, for example the publication Kemian teollisuus (Chemical Industry) 28 (1971) 2/97-101.
Modern applications of polymeric materials often require resistance to heat and thermal stability, both over a very wide range, and in particular long-term weather-resistance also in difficult and extreme conditions and in rapidly changing extreme conditions. This is especially true regarding technical textiles and products made from them, for example buildings and structures, and in particular when they are used under arctic or tropical conditions.
It is known that the mechanical properties of polyimides usually remain unchanged when the external temperature varies even by 600.degree.-700.degree. C. For example, at a temperature of 500.degree. C. a polyimide film is twice as strong as a polyethylene film is at room temperature. Its strength at room temperature is approximately the same as that of polyethylene terephthalate film, but considerably greater below 0.degree. C. A polyimide film does not soften or melt, and its elasticity remains, between the temperatures -200.degree. C. and +400.degree. C.
On the basis of the above it is evident that aromatic polyimides are especially well suited for the coating of textiles which must be weather-resistant under very difficult and extreme conditions. Aromatic polyimides are, however, very expensive, and if they are used for coating textiles which are also required to be waterproof, they must be used in very large quantities, whereby the price of the product rises immoderately high.
The object of the present invention is thus to provide a waterproof and at the same time weather-resistant and substantially non-stretching textile with a more economical price, the textile being a substantially non-stretching, tension-resistant cloth coated with a smaller amount of weather-resistant synthetic substance than previously, as well as a method for producing such a textile.
The object of the present invention is, furthermore, to provide a waterproof and at the same time weather-resistant and substantially non-stretching, rollable textile component, intended for use for parts of a building or a structure which are subject to loads, the component being a substantially non-stretching, tension-resistant cloth coated with a smaller amount of weather-resistant synthetic substance than previously.